1. Field of the Invention
The present invention relates to a method of positioning a head and a disk apparatus for the same, and more particularly, to a method in which the position of a head can be automatically adjusted or corrected and a disk apparatus for the same.
2. Description of the Related Art
In a conventional recording system, for example, a magnetic disk recording system, the position of a head is designated by a host. FIG. 1 is a block diagram showing the conventional magnetic disk recording system. As shown in FIG. 1, the magnetic disk recording system includes a host unit 100 and a disk apparatus 102. The host unit 100 outputs an external step pulse signal 131 shown in FIG. 2B and an external direction signal 132 shown in FIG. 2C to the disk apparatus 102. The external step pulse signal 131 includes one or more pulses each of which corresponds to one track. The external direction signal 132 is in a high level, i.e., "H" level when the direction toward the outermost track is designated and is in a low level, i.e., "L" level when the direction toward the innermost track is designated. The external step pulse signal 131 and the external direction signal 132 are received by a drive circuit 135 of the disk apparatus 102. The drive circuit 135 generates a driving signal based on these signals 131 and 132 and drives a motor 137 such as a stepping motor to move a head (not shown) by one track in a direction designated by the external direction signal 132 in response to each of pulses of the external step pulse signal 131. Thus, the head can be positioned on a desired track position. The external step pulse signal 131 and the external direction signal 132 are also supplied to a track counter 134 of the disk apparatus 102. When the external direction signal 132 is in the L level, the track counter 134 counts up in response to each of the pulses of the external step pulse signal 131 and when the external direction signal 132 is in the H level, it counts down in response to each pulse of the external step pulse signal 131, as shown in FIG. 2D. The track counter 134 is reset by a track 0 signal. The track 0 detector 133 detects that the head is positioned in the vicinity of the track of track number 0, i.e., the outermost track in this example, and generates a track 0 detection signal as shown in FIG. 2E. A circuit 138 receives the external direction signal 132, the track 0 detection signal from the track 0 detector 133, and the driving signal 136 from the drive circuit 135 to generate the track 0 signal 139 as shown in FIG. 2F. The track 0 signal 139 is set to the active L level in response to the drive signal 136 when the track 0 detection signal 142 and the direction signal 132 are both in the L level, and it is reset in response to the drive signal toward the innermost track when the track 0 signal is set. The track 0 signal is supplied to the host unit 100 in addition to the track counter 134. An insertion detector 130 generates an insertion detection signal 141 when a disk is inserted or loaded into the disk apparatus 102. The insertion detection signal is not used for control of the movement of the head in the conventional disk apparatus 102 but only for other processing.
Next, the operation of the conventional magnetic disk recording apparatus will be described below with reference to FIGS. 2A to 2G. It is assumed that the head is now positioned on the track position of track number 3 of the disk. Since the external direction signal 132 is in the H level, the track counter 134 receives the pulses of the external step pulse signal 131 from the host unit 100 to count down so that the count is 2, as shown in FIG. 2D. Also, the drive circuit 135 receives the external step pulse signal 131 and the external direction signal 132 to drive the motor 137 such that the head is positioned on the track position of track number 2, as shown in FIG. 2G. Subsequently, the same operation is repeated each time each of the pulses of the external step pulse signal 131 is supplied. When the head is moved close to the outermost track; i.e., the track position of track number 0, the track 0 detector 133 detects that the head is positioned in the vicinity of the outermost track and generates the track 0 detection signal 142 of the L level as shown in FIG. 2E. At this time, if the direction signal 132 is in the H level, the track 0 signal 139 is set to the L level in response to a pulse of the driving signal 136 from the drive circuit 135 and held in the L level until the next pulse of the drive signal 136 is supplied to the circuit 138. The track 0 signal 139 is supplied to the host unit 100. At this time, the head is positioned on the track position of track number 0.
When the external direction signal 132 of the L level is supplied to the disk apparatus 102 from the host unit 100 in response to the track 0 signal 139, the track counter 134 counts up to 3 in response to each of the pulses of the external step pulse signal 131. At the same time, the head is sequentially moved toward the innermost track one track by one track to position on the track position of track number 3.
It is assumed that in such a state the disk is ejected so that the insertion detection signal 141 changes from the H level to the L level. In this case, the head is often moved because of mechanical impact. If the head is mechanically moved to the track position of track number 1, when one pulse of the external step pulse signal 131 is supplied, the count of the track counter is counted up to 4, as shown in FIG. 2D. However, the head is actually positioned on the track position of track number 2, as shown in FIG. 2G.
As described above, in the conventional disk apparatus, there is a problem, in that the read/write operation is made impossible when the head position is moved because of mechanical impact.